Hello Sir,
I'm only a shade-tree self-taught mechanic, and I'm not an axle expert, but thought I'd throw my 2 cents in just in case it helps any. I bought the exact same axle, an S-9000, to convert my Loadstar 1700 to 4wd. There is some info about it at the end of this thread:
viewtopic.php?f=26&t=9172 The IH axle code for the S-9000 is either a FA64 or FA78. I have not found any difference in the IH parts manuals between these two.
Per the IH parts manuals, there were several ratios available. And most of those ring and pinions have the same part numbers as used in a rear RA30 axle so that tells me the RA30 carrier assembly was used in these S-9000 axles. But here is the actual list of R&P ratios listed for this front axle:
IH Part Number: R&P Ratio: R&P Number of teeth:
P/N: 69-021-R93 .... Ratio: 5.29 ... Teeth: 37-7
P/N: 578-793-C91 .. Ratio: 5.38 ... Teeth: 43-8
P/N: 69-022-R93 .... Ratio: 6.17 ... Teeth: 37-6
P/N: 69-014-R93 .... Ratio: 6.67 ... Teeth: 40-6
P/N: 69-015-R93 .... Ratio: 7.17 ... Teeth: 43-6
The above ratios are listed for the FA64 axles and FA78 axles and RA30 axles. In addition the P/N 1653808C91 for ratio 4.78 is listed for the RA30.
Weller axle remanufacturing in their catalog last revised in 2011 lists the following ratios as available: 5.29, 5.38, 6.17, 6.67, and 7.17. However I've found Weller to be very expensive. I wanted to buy a transmission gear from them and they wanted $1,000.00 for the trans gear. So it's anyone's guess what they might want for a R&P gear set. There is another supplier, New-Star, that sells replacement ring gear and pinion sets. Their latest catalog update (which has no date) lists 3 ratios available: 5.38, 6.17, and 7.17.
Your rear axle is different than mine so I can't tell you anything about it. But if I knew your IH axle code, I could probably look up in the parts book for information like I did for your front axle. And speaking of axle codes, I don't know if anyone has mentioned the Wisconsin Historical Society to you ... for a few dollars and your vehicle's vin number, they will send you a print-out of all the components and options your particular truck came with from the factory - including axle codes, axle ratios, engine, transmission, brakes, etc. etc.
As far as wheels go, I wanted to put some Michelin XZL's on my truck, one at each corner. It's a 46 in tall radial tire that costs $1200 to $1400.00 each new but can be had for $200 to $400 each from military surplus suppliers. Even when unused, the military must throw them away once they are 4 years old. I've just heard so many good things about this tire. And there is a company that will make rims for this 20 inch tire to fit our Dayton spoke hubs. Unfortunately I don't recall the name of that company, but I'm sure I could find it again with google searches.
Unlike most people on this site, I'm no truck mechanical expert and have little actual experience, but just wanted to give you a few more possibilities to think about.
I was just wondering, do you know if your truck came from the factory as 4wd? The bottom axle U-bolt plate looks home made and does not look at all like the factory-made U-bolt plate. Also I thought, although I could be mistaken, that the S-9000 axle was made for the S-Series of IH trucks.
Would sure like to see more pics of your truck. Once mechanically restored, I think you will find this to be a very capable, off and on-road dependable truck. I would not hesitate to take it anywhere wilderness camping. I look forward to when my truck is finished and I can take it 4x4 camping.
I'd like to ask a favor, could you please take some pictures of your spring hangers and steering box pitman arm and drag link? I've never actually seen one of these axles mounted to a Loadstar 1700. And if you install a diesel, would you want to sell your engine? I'm looking for a complete, good-running gas 345 V8.
Thank you